It is known that bis-(alkoxysilylalkyl)-oligosulphides can be produced from the corresponding alkoxy silyl alkyl mercaptans by direct reaction with sulphur (German Patent No. 2,405,758 and related Pletka U.S. Pat. No. 3,997,581. The entire disclosure of Pletka is hereby incorporated by reference and relied upon.) The same oligosulphidic silanes can be obtained even more simply and conveniently from the alkoxy silyl alkyl halides by a single reaction with, in particular, alkali metal hydrogen sulphides and sulphur. In this case, excess hydrogen sulphide is formed (German Offenlegungsschrift No. 2,542,534 and related Pletka U.S. Pat. No. 4,072,701. The entire disclosure of this Pletka patent is hereby incorporated by reference and relied upon.)
It is also known that bis-(alkoxysilylalkyl)-oligosulphides can be produced from the corresponding disulphides by reaction with sulphur at temperatures in the range from 100.degree. to 200.degree. C. (German Offenlegungsschrift No. 2,360,471).
All the above-mentioned oligosulphides contain up to at most 6 sulphur atoms forming as it were a bridge between the two alkyl groups attached to the silicon, the alkyl groups containing from 1 to 10 carbon atoms.
Finally, it is known that silyl alkyl thioethers can be obtained from vinyl silanes by reaction with hydrogen sulphide (German Auslegeschrift No. 1,000,817).
Oligosulphidic silanes have acquired considerable significance as additives in rubber mixtures containing silica filler inter alia for improving the mechanical properties of the vulcanisates (German Patent No. 2,555,577 and related Thurn U.S. Pat. No. 3,873,489. The entire disclosure of Thurn is hereby incorporated by reference and relied upon.)
It is also possible to introduce sulphur-free silanes containing unsaturated organic groups as ligand on the silicon atom into mixtures based on certain rubbers. It is also known that silyl alkyl thioethers do not produce any advantageous rubber properties in vulcanisates and that, among other disadvantages, mercapto silanes give off an intense, very unpleasant odor.
An object of the present invention is to provide a new and useful process for the production of sulphur-containing silanes which may be easily and effectively incorporated for example into rubber mixtures containing silicate fillers and which inter alia impart particularly favorable properties to the vulcanisates obtained therefrom.
Another object is to develop novel sulphur containing silanes.
A further object is to prepare novel rubber mixtures containing such sulphur containing silanes and silicate fillers with or without sulphur and with or without carbon black.